Thermionic valve circuits



Aug. 21, 1945. Q G. J. s oLEs 2,383,420

- THERMI'ONI-C VALVE'CIRCUIT Filed Sept. 21, 1943 To V/'a'e0 Stage 7bAudio Stage Patented Aug. 21, 1945 ,l v 2333 4201 THERMI'ONIG VALVECIRCUITS GrahamJohn SGOIeS EaSt sheentsLondon, En land, assigncr ,to,Metropolitan vickers,Electri-r cal Company Limited, L ndon,..En'gland,.a com:

pany of GreatBrltain Applicationvseptember 21, 1943;;Seria1;No;:503;280lnyfireateBnit l iit ihrlflilsi 2 Claims; (CL

h oinvehtiontlt lateaetogthermionic.valvelcire r ficationzarezzapplied,:whilstthe.cathode of this cuits,;and specificallstoysoecalledpdimitcrscircuitsau, diodeziszconnected-totthe earthyfbusbar of the Thet ite rtionc'is znotablyi-but not exclusively, apesignahinput-v circuit; through two resistances -in pl-icable --in;circu-its wherein-z:,fromecomplexrorn, seriessdwhich. may becollectively bridged by a 5 t-tsmoothin'g. condenser) the junction ofsaid two re 'de 'vedubYgmeansrof ta ,detectorzdevice s resistancesbeingi connectedto the-anode of the a The inyentiongisgapplicable;..in:the limiter:.-diode-and througha condenser to said v .-,.ca. lledr.,panoramicii; radio-treceivers; busbanl-the'-cathode-of:the limiterdiode being thetnature z f whic.hcwas-describedinfifElectrone"maintainednatran:appropriate positive potential ics Jun940,and-,-wherein imbrief. a waveband,.alor bonveniently bybeingconnected to the junction or dt rn be -an selectedcbnexof at-pluralityznf, 2 point, oiatwo: further-resistances connected"bewaveba-nd slscanned fromuendtto ;;,end--by.,the, tween a source ofpositive potential and-said automat c;variationtp a tuning-parameter:busba'r. Of these resistances, the one connected a rate comparable withthe frequency of ,theuperw between-the; cathodeiand busbar: of thelimiter sistenceyofgyision; :the.- output;,or outputs due to l dio'demay be variable The-anodeofthe limiter any received radio transmissionswhich may be difideiisiconnectedwalsO.,to'-the .vide0 amplifier-ortaking place within the waveband being indiother utilisation circuit.The output from the Gat s resonance P Components p pe detector diode mayalso be taken from a tapping dicular-to a time base waveband componenton (which, may be variable) on that of the firstthe screen of a cathoderay tube, the time base mentioned two resistances which is connected pnent being provided sy r y Wit to the aforesaid busbar, and applied, forexample, the scanning such as by means of a saw-tooth to an audiofrequency amplifier.

yp of oscillation generator. Provision can be With the known arrangementjust above demade whereby any Selecte o e of the thus i scribed, if thepotential across the detector recated transmissions can be t ned inmanually sistance between the limiter diode anode and and its modulationlistened to or recorded or busbar becomes greater tha th t across th ote w e indicated, that is to say, the Scanning resistance connectedbetween the busbar. and the of the waveband can be effected ole y y handcathode of the limiter diode, then the latter valve tsuch as through theturning o a knob about an conducts and prevents further increase ofoutput,

, thereof, provides a detector arrangement whereby associated dialindicat the wavelength- In but for satisfactory operation this largelydesuch a panoramic receiver it has been convenient pends upon theinherent poor regulation of t for the purpose of the rapid scanning ofthe diode detector circuit WaVebaIld t0 the Value of certain tuning Thepresent invention comprises a thermionic components of the oscillatorsection of a fre- 5 valve circuit for detecting complex signals,

quency {hanger. valve in superheiemdyne wherefrom the different outputsare respectively with Whlch Superheterodyne clrcult preferably extractedby a detector arrangement adapted to has thrge of fliequency changing wlimit at least one of said outputs to approxirespondlng intermed atefrequency circuits, and mately a predetermined value Without limitingpreferably the Scanning 1S effected by reactor another output oroutputs, the detector valve valve associated with the second oscillatorbeing arranged as a per Se Well known cathode through an amplifier asdescribed in copendlng follower or infinite impedance" type, and haw g zgfig$3 5}: gi jii f gg ffi g gw ing its cathode connected through a highresistance to the anode of a limiter diode, the cathode The presentmventmn accordmg tonne aspect of which is positively biased. Saidresistance one of the several outputs therefrom,such as'the must be highcompared with the impedance of the diode. video output, is llmlted toapproximately a predetermined value without, however, another outtype ofdetect r used 1n thepresent mven put or other outputs, such as an audiooutput, non fi o regulatmn so that Its Output V0115- being 1i it d ageis largely-independent of the cathode load that good response isobtained A know llmlter arrangement (see Brltlsh and $0 armflgedSpecificatifn No. 474,356) comprises a diode rec- D t the hi h r quen eswhich it s desired tifier followed by a diode limiter such as for the te clrcult shall eal w th. Smce the feed video output from the detectordiode, to the resistance from the detector cathode to the l manode ofwhich the signals, after suitable ampliiter diode anode is high comparedwith the 1mpedance of this valve, the output voltage from the limiter islimited to that of the cathode thereof, while the limiter circuit as awhole has no effect upon the output, such as audio output, which may betaken direct from the detector, in the known manner above described, andsuch is partly due to the relative impedances of the two circuits andpartly due'to the inherent good regulation of the cathode followercircuit.

It will be appreciated that there may be provided more than one limitercircuit.

The single figure of the accompanying drawing is a circuit diagramillustrating the invention, and it will be seen that the detector valveVI is of the cathode follower type having its cathode connected to theearthy busbar B through the resistance R. in series with thepotentiometer resistance RI across which latter is the condenser CI,whilst a condenser C2 is connectedacross both resistances, the radiofrequency input to the valve VI being applied between the control gridA'and the busbar B. The cathode of the valve VI is connected through thehigh resistance R2 to the anode of the diode V2 and to the video stagesuch as indicated at Vid. A in Fig. l of the drawings of mycopending U.S. application Ser.

terminals and for limiting at least one of said outputs to approximatelya predetermined value without limiting audio output, comprising adetector valve having a cathode and a signal receiving grid and arrangedas a cathode follower, a limiter diode having an anode and a cathode,means including a resistance connecting the cathode of the detectorvalve to the anode of the limiter diode, said resistance being highrelatively to the impedance of the limiter diode, and the cathode of thelimiter diode being positively biased, means for taking the limitedsignal output from the anode of the limiter diode, a resistance in thecathode circuit of the detector valve, and means for taking anothersignal output from said last named resistance.

No. 503,278, filed of even date herewith, whilst 2. A thermionic valvecircuit for detecting complex signals, comprising a detector valvehaving a radio frequency input grid connected to one terminal of thecircuit and a cathode coupled by a resistance to the other terminal ofthe circuit, a limiter diode having an anode and a cath ode, meansincluding a resistance connecting the junction of said series-connectedresistances and the cathode of the limiter diode, and means for taking asignal output from said first-mentioned resistance.

GRAHAM JOHN SCOLES.

